#1
For you smart people out there. It's about science.
So we had a science exam today. **** it was hard. I'm year 10, 2nd year at high school, and I didn't expect it to be this hard. Like, I wrote down one question to see if any other 15 year old could figure it out.

"Determine the molecular formula of an oxide of carbon that is made when 23.67g of carbon is combined with oxygen to produce 86.79g of the oxide. The molar mass of the compound is 44.0 gmol-1. Show all of your working."

I realise now that the oxide of carbon is most probably carbon dioxide, or carbon monoxide. But I was damn confused and wiped during the exam.
#3
Quote by iamded
For you smart people out there. It's about science.
So we had a science exam today. **** it was hard. I'm year 10, 2nd year at high school, and I didn't expect it to be this hard. Like, I wrote down one question to see if any other 15 year old could figure it out.

"Determine the molecular formula of an oxide of carbon that is made when 23.67g of carbon is combined with oxygen to produce 86.79g of the oxide. The molar mass of the compound is 44.0 gmol-1. Show all of your working."


Well thats a piece of piss to work out should you know how to do it... The steps are simple.

I can tell you before you work it out its Carbon Dioxide because the molar mass is 44 (12 +16 + 16 = 44)

But we will do it mathematically.

You have a mass of 23.67g of carbon. 12g of carbon is 1 mole therefore in 23.67 you have

23.67/12 = 1.9725

The molar mass of the compound is 86.79, so - 23.67 = 63.12

In one mole of oxide there is 16 grams of oxygen.

63.12/16 = 3.945

C= 1.9725
O= 3.945

C= 2
O= 4

Divide both by 2 and you get CO2

The molecular formula of carbon dioxide.

Edit:

You divide by 2 to get the lowest ratio of the atoms in the molecule.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#4
23.67g of C = 1.97 moles
that means you will have 1.97 moles of the oxide.
If this was CO2, then weight will be (12 + 2x 16) x 1.97 = 86.79, which is what's given
therefore it's CO2

edit: yeah- his way- I took ages because for some reason I thought M(C) = 14gmol-1
Who reads sigs anyway
#5
Oh. Well that makes sense. Thanks, and btw, you're not doing my work for me, the exam's kinda over.
Thanks for explaining though, I get it now. I was baffled during the exam, and I bet there's a hell of a lot of UG'ers that couldn't figure that out.
#6
Quote by iamded
Oh. Well that makes sense. Thanks, and btw, you're not doing my work for me, the exam's kinda over.
Thanks for explaining though, I get it now. I was baffled during the exam, and I bet there's a hell of a lot of UG'ers that couldn't figure that out.


That would be me.
Haha.
Our hearts are with Nick Grundy.
Quote by Ez0ph
I think AvengedThrice is pretty cool guy, eh raeps kittens to death and doesn't afraid of anything.

He knows me well..
#7
wow i got an A in chemistry only 3 years ago doing this stuff. and just looking at that now makes my brain hurt. just shows how useless school really is.